In an automotive vehicle with dual front-seat air bags, it is desirable to sense or detect whether or not the passenger seat is occupied. In the event that the passenger seat is unoccupied, it is desirable to avoid activation of the passenger-side air bag in the event of vehicle impact to reduce repair costs. More importantly, it is desirable to determine if the passenger side of the front-seat is occupied by a rear-facing infant seat so that activation of the air bag can be inhibited to prevent injury to the infant. Under current practice, operators of vehicles equipped with dual front-seat air bags are advised to place the infant seat in the rear vehicle seat. However, this advice often is unheeded, risking injury to the infant by deployment of the passenger-side air bag when the infant seat is placed in the front vehicle seat.
It is therefore a general object of the present invention to control deployment of a passenger-side air bag as a function of occupancy of the passenger side of the front seat. It is a more specific object of the present invention to provide a method and system to prevent deployment of the front-seat passenger-side air bag in a dual air bag system when the passenger seat is unoccupied, or when the passenger seat is occupied by a rear-facing infant seat. Another and related object in accordance with one aspect of the present invention is to provide an infant seat having facility for cooperation with a vehicle supplemental restraint system to prevent activation of the passenger-side air bag when the infant seat is disposed in a rear-facing orientation on the passenger side of the front seat.
An automotive vehicle supplemental restraint system in accordance with the present invention includes an air bag positioned within the vehicle opposite a predetermined seat position such as the passenger side of the front seat, and electronics coupled to one or more impact sensors for activating the air bag in the event of a vehicle impact. One or more occupancy sensors are provided at the passenger seat for sensing seat occupancy and inhibiting activation of the air bag when the seat is either unoccupied or occupied by a rear-facing infant seat. In the preferred embodiment of the invention, system status is displayed to a vehicle operator, and the operator is provided with an opportunity to override the occupancy sensors and enable activation of the air bag.
In one form of the invention, the occupancy sensors take the form of a first sensor for detecting seat occupancy as a function of weight supported by the seat, and a second sensor responsive to disposition of an infant seat in a rear-facing orientation. This second sensor preferably comprises a magnetic switch disposed in the passenger seat and a magnet at a predetermined position in the infant seat for activating the magnetic switch when the infant seat is disposed in a rearwardly facing orientation, and not activating the magnetic switch when the infant seat is disposed in other than a rearwardly facing orientation. The weight sensor in this embodiment of the invention comprises a normally open switch that assumes a closed condition responsive to occupant weight, and the magnetic switch comprises a normally closed switch that opens responsive to the infant seat magnet. The weight switch and the magnetic switch are connected in series so as to enable activation of the air bag when both switches are closed.
In another embodiment of the invention, the occupancy sensor comprises a plurality of weight sensors disposed in an array at the monitored seat position. In the preferred form of this embodiment, each sensor comprises a permanent magnet and a linear Hall effect sensor underlying the magnet and separated from the magnet by a resilient element such as a foam rubber pad. The array of sensors provide analog signals to an analyzer circuit which collectively provide information about seat occupancy. The analyzer circuit is programmed or calibrated to distinguish between an unoccupied seat, a seat occupied by a forward-facing passenger of any size, and a seat occupied by a rear-facing infant seat, for example.
In other embodiments of the invention, optically readable indicia, preferably in the form of reflectors or vertical code bars, is disposed on the passenger seat back and/or on the back of an infant seat. An optical sensor is mounted beneath or within the vehicle dashboard opposite the passenger-side front seat, and is connected to air bag control electronics for inhibiting activation of the air bag when the optically readable indicia is detected on either the infant seat or the passenger seat back. The optically readable indicia preferably is provided both on the back rest of the passenger-side front seat, and on the back of the infant seat. When a passenger occupies the seat, the body of the passenger blocks reading of the indicia on the seat back, so that the reader does not detect such indicia and deployment of the passenger-side air bag is enabled. Placement of an infant seat on the passenger-side front seat also blocks the indicia on the back of the passenger seat. However, the indicia is also provided on the back of the infant seat, so that the reader detects such indicia and inhibits deployment of the passenger-side air bag as if the seat were unoccupied.
In accordance with another aspect of the present invention, there is provided an infant seat having a base, a generally L-shaped seat structure with an interior for holding an infant, and a seat back. In one embodiment, a magnet is disposed within the base of the infant seat for cooperation with a magnetic sensor in a vehicle seat to detect orientation of the infant seat when placed in the vehicle. In another embodiment of the invention, optically readable indicia is permanently exteriorly affixed to the seat back and oriented to face the vehicle dashboard when the seat is positioned in a vehicle passenger-side front seat with the interior of the seat facing rearwardly.